Fuse construction



May 30, 1950 Filed June 4. 1947 A. G. STEINMAYER ET AL FUSE CONSTRUCTION 2 Sheets-Sheet 1 IN V EN TORS L MWMQ May 30, 1950 A. G. STEINMMERV ETAL 2,509,892

FUSE CONSTRUCTION Filed June 4, 1947 2 Sheets-Sheet 2 .l'lfl' I F16. Z Q 1| l du" 57 w WWM Patented May 30, 1950Y orales russ coNsTaUc'rToN f Alwin G. Steinmayer, Milwaukee, and William 0. Schultz, South Milwaukee, Wis., assiznors to McGraw Electric Company, a corporation of Delaware Application Julie 4, 1947, Serial No. 752,516

2 claims. l

smaller overloads of a value which might ulti-V mately injure the transformer or other device, and to so organize the device that the circuit is finally interrupted by a i'use which, after a given time delay, is suddenly overloaded.

In greater detail, further objects are to provide a bi-metal controlled fuse construction which normally provides parallel paths but which, on sustained small overloads, finally removes one of the paths and limits the current to a single path through a fuse whose rating is much below the small overload current thereby causing substantially instantaneous rupture of the fuse and opening of the circuit. i

Further objects are to provide a bi-metal controlled switch which is normally closed and which suddenly opens when the bi-metal is heated to a predetermined degree by the sustained small overload current, and which opens one oi the parallel paths as described above and causes all of the current to iiow through a fuse which immediately ruptures, and 'to so construct the switch that it remains open after the bi-metal has cooled and has to be manually reset.

An embodiment of the invention is shown in the accompanying drawings, in which:

Figure 1 is a sectional view showing a further form of the invention and illustrating` how the invention may be applied to a housed type of fuse structure, such view showing the parts in their normal position.

Figure 2 is a view corresponding to Figure 1 and partly in section showing the position of the parts after operation of the device.

The fuse comprises a housing 54 and a door 55 hinged thereto in a well known manner, See Figure 2. The door slidably carries a drop-out fuse tube 56 which is provided with a fuse link indicated generally by the reference character 51 whose upper end is electrically connected to the upper terminal 58 of the fuse tube and whose lower end is electrically connected to a latching lever 59. This latching lever 59 normally engages a metallic iitting 60 supported from the door 55 and when the fuse link blows it throws out any remaining portion of the fuse link and releases the fuse tube 56 and allows such fuse tube to slide downwardly as shown in Figure 2.

(Cl. 20o-114) The housing carries a stationary upper terminal 6I adapted to be connected to the line wire and a stationary 1ower terminal 62 adapted to be connected to the load. The stationary upper terminal 6i normally engages the upper terminal 58 of the fuse tube 56. The lower stationary terminal 62 engages a terminal 63 carried by the door and through which the fuse tube 66 is adapted to slide. The terminal 63 carries a bimetal member 64 which is provided with a stop 65 against which a shouldered portion of the hub part 66 of a switch 61 normally bears. The free end of the bi-metal member which carries the stop 66 is connected by means of flexible leaders 69 and 66 with the switch 61 and with the lower fitting 60. The switch arm 61 normally bears against a rib or contact 10 formed integrally with the upper terminal 58 of the fuse tube.

It is to be noted that the switch 61 is urged towards open position by means of the spring 1| and is normally held in closed position by means of the bi-metal member 64 coacting with the hub portion 66. 'When the switch is released as hereinafter described, it swings in a clockwise direction away from the contact portion 'l0 of the upper fuse terminal 58 and the door is provided with a recessed upper portion 12 to accommodate the switch. 'Ihe door, if desired, may be tapered inwardly towards its lower portion as shown, and thus will also provide a. housing or space for the bi-metal member 64 and the iiexible conducting tapes 68 and 69.

From the description it will be apparent that I the current iindsparallel paths from the upper line terminal 6I to the lower load terminal 62. One of the paths is through the fuse link 51 to the lower iitting 60, through the flexible conductor 68, through the bi-metal member 6l to the terminals 63 and 62. The other path is from the line terminal 6I through the switch 61 through the conducting exible member 69 through the bi-metal member 64 to the terminals 63 and 62. On heavy short circuits the fuse ruptures and the switch 61 opens. However, on sustained small overloads the bi-metal member 6l heats up and releases the Switch 61. All of the current now has to pass through the fuse link whose current carrying capacity is much less than the small overload current. Consequently, the fuse link immediately ruptures and clears the circuit, the fuse tube moving to drop-out position as shown in Figure 8.

It will be seen that all of the current passes f through the bi-metal member and that two paths are normally provided in parallel from the line terminal to the load terminal.

It will be seen also that on sustained small overloads means are provided for opening one o! the parallel paths andl forcing the current to traverses single path .whose current carrying capacity is so chosen that it immediately ruptures and clears the circuit.

It will be seen also that when the bi-metal member cools, that the switch does not reclose but remains open and has to be manually reset.

-Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

We claim:

1. A drop-out fuse construction comprising a drop-out fuse tube, a fuse link therein, an upper and a lower stationary terminal normally electrically connected by said fuse link, switch means normally bridging said fuse link and biased towards open position, and means responsive to a sustained current o! a predetermined value normally restraining said switch means and arranged to release said switch means upon response to said current oi' predetermined value, said fuse link having a current carrying capacity less than that of said current of predetermined value.I

2. A housed drop-out i'use construction comprising a housing having an upper and a lower stationary terminal, a door for said housing, a fuse tube slidably carried by said door and biased towards downward sliding motion andhaving an upper terminal normally engaging the upper stationary terminal, a fuse link extending from the upper terminal of said fuse tube downwardly through said fuse tube and electrically connected toA said lower stationary terminal, restraining means restraining said tube against drop-out motion and controlled by said fuse link and releasable upon rupture of said fuse link. a switch carried by said door biased towards opening motion and normally engaging the upper terminal of said fuse tube, said switch being electrically connected to said lower stationary terminal, and bimetal means carried by said door and arranged to normally hold said switch in contact with the upper terminal of said fuse tube. said bi-metal means being arranged to carry the total current passing through said fuse link and said switch and to release said switch when energized by a sustained current of a predetermined value larer than that required to rupture said fuse link.

ALWIN G. STEINMAYER. WILLIAM O. SCHULTZ.

REFERENCES CITED Name Date Hart Dec. 14, 1937 Number 

